1. Field of the Invention
The present invention relates to a bladed rotor such as an impeller of a torque converter and an apparatus for producing such a bladed rotor.
2. Description of the Prior Art
An example of a prior art bladed rotor is disclosed in Japanese Patent Provisional Publication No. 51-92965. The rotor consists of a shell, a core and a plurality of blades connected to the shell and core. The connection of the blades to the shell is attained by fitting the fingers of the blades which are provided to the shell engaged edge thereof, in the narrow, elongated depressions of the shell. Further, the connection of the blades to the core is attained by fitting the fingers of the blades which are provided to the core engaged edge thereof, in the slits of the core. The depressions of the shell and the slits of the core are constructed and arranged so as to be formable by punches and dies through relative movements thereof in parallel to the axis of rotation of the bladed rotor so that the forming of the depressions of the shell and the slits of the core as well as the installation of the blades to the shell and the core can be attained with ease.
However, in such a prior art bladed rotor of the kind in which each of its blades has flatly curved side surfaces, the depressions and the slits provided to the shell and the core are arranged so as to have, with respect to a plan view, longitudinal axes which do not coincide with the straight lines extending radially through the centers of the shell and the core but make certain angles therewith. Due to this, the punches for forming such depressions and slits have a difficulty in uniformly pushing the surfaces of the shell and the core against the dies but are subjected to bending forces, thus being liable to be broken easily and therefore shortening the lives of the die assemblies for forming such depressions and slits. Further, it is difficult to give sharp corners to such depressions due to irregular contact of the punches to the surface of the shell, thus causing a poor holding ability with which the blades are held by the depressions.